2.0.4 patch

- Updating SalesforceCommonUtils to fix an issue with base app ID in iOS 7 (hopefully a fix to [Issue #432](https://github.com/forcedotcom/SalesforceMobileSDK-iOS/issues/432)).
- Adding token revocation on the service back to logout; looks like it fell through the cracks in the 2.0 release.
- Fixing thread safety issue in RestKit/SFRestAPI ([Issue #407](https://github.com/forcedotcom/SalesforceMobileSDK-iOS/issues/407)).